package com.example.util;

import java.net.InetAddress;
import java.net.UnknownHostException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.Random;

/**生成唯一的GUID
 *
 * @email: pengyujun53@163.com
 * @author: peng_YuJun
 * @date: 2023/3/11
 * @time: 17:39
 */
public class RandomGUID {

    public String valueBeforeMD5 = "";
    public String valueAfterMD5 = "";
    private static Random myRand;
    private static SecureRandom mySecureRand;

    private static String s_id;
    private static final int PAD_BELOW = 0x10;
    private static final int TWO_BYTES = 0xFF;

    static {
        mySecureRand = new SecureRandom();
        long secureInitializer = mySecureRand.nextLong();
        myRand = new Random(secureInitializer);
        new Thread(new Runnable() {
            public void run() {
                try {
                    s_id = InetAddress.getLocalHost().toString();
                } catch (UnknownHostException e) {
                    e.printStackTrace();
                }
            }
        }).start();
    }

    /**
     * 获取随机生成的GUID
     * @return
     */
    public static String getRandomGUID() {
        return new RandomGUID().toString();
    }

    public RandomGUID() {
        getRandomGUID(false);
    }
    public RandomGUID(boolean secure) {
        getRandomGUID(secure);
    }

    /*
     * Method to generate the random GUID
     */
    private void getRandomGUID(boolean secure) {
        MessageDigest md5 = null;
        StringBuffer sbValueBeforeMD5 = new StringBuffer(128);

        try {
            md5 = MessageDigest.getInstance("MD5");
        } catch (NoSuchAlgorithmException e) {

        }
        try {
            long time = System.currentTimeMillis();
            long rand = 0;

            if (secure) {
                rand = mySecureRand.nextLong();
            } else {
                rand = myRand.nextLong();
            }
            sbValueBeforeMD5.append(s_id);
            sbValueBeforeMD5.append(":");
            sbValueBeforeMD5.append(time);
            sbValueBeforeMD5.append(":");
            sbValueBeforeMD5.append(rand);

            valueBeforeMD5 = sbValueBeforeMD5.toString();
            md5.update(valueBeforeMD5.getBytes());

            byte[] array = md5.digest();
            StringBuffer sb = new StringBuffer(32);
            for (byte b1 : array) {
                int b = b1 & TWO_BYTES;
                if (b < PAD_BELOW)
                    sb.append('0');
                sb.append(Integer.toHexString(b));
            }

            valueAfterMD5 = sb.toString();

        } catch (Exception e) {

        }
    }

    public String toString() {
        String raw = valueAfterMD5.toUpperCase();
        StringBuffer sb = new StringBuffer(64);
        sb.append(raw, 0, 8);
        sb.append("-");
        sb.append(raw, 8, 12);
        sb.append("-");
        sb.append(raw, 12, 16);
        sb.append("-");
        sb.append(raw, 16, 20);
        sb.append("-");
        sb.append(raw.substring(20));

        return sb.toString();
    }
}
